Various medical procedures require the sequential administration of different fluids. For example, administration of the cardiac drug known as Adenosine must be followed immediately by the administration of a normal saline solution in order to get the drug into circulation rapidly. Heretofore the sequential administration of different fluids has been accomplished utilizing two syringes, one loaded with the first fluid to be administered and the other loaded with the second fluid to be administered. The two needle system is not only awkward but also increases the risk that medical personnel will suffer inadvertent needlesticks.
A previous attempt to solve the foregoing problem is shown and described in published U.S. patent application Ser. No. 2002-0035351-A1. Referring to FIG. 1 of the present application, the device disclosed in the published application comprises a single barrel double chamber syringe 10 having a barrel 1 and a plunger 2 which is utilized in the conventional manner to force fluids contained within the barrel 1 outwardly through a hollow needle 8. This is accomplished by means of a push stopper 3 secured to the plunger 2 and made of a pliable material to maintain a fluid tight seal around its outer periphery. A hollow floating plunger 5 situated within the barrel 1 is likewise comprised of a pliable material to maintain a fluid tight seal around its outer periphery. The floating plunger 5 divides the barrel 1 into a first compartment 4 and a second compartment 6.
The hollow needle 8 is secured in a hub 9 situated at the opposite end of the barrel 1 from the plunger 2. The hollow needle 8 comprises a first component extending outwardly from the barrel 1 and the hub 9 and a piercing component extending from the hub 9 into the second compartment 6 of the barrel 1. The hollow needle 8 is provided with a porthole 7 to assure full delivery of fluid contained within the second compartment 6.
In the operation of the syringe 10 a first fluid is loaded into the second compartment 6 and a second fluid is loaded into the first compartment 4. As the push stopper 3 is forced downwardly (FIG. 1) into the barrel 1 under the action of the plunger 2, the fluid within the first compartment 4 and the floating plunger 5 function to force the first fluid outwardly from the second compartment 6 through the hollow needle 8. As the floating plunger 5 moves downwardly it eventually engages the piercing component of the hollow needle 8 which begins to penetrate the floating compartment 5. Meanwhile, the remainder of the first fluid is forced out of the second compartment 6 through the porthole 7 and the hollow needle 8.
Continued downward movement of the push stopper 3 under the action of a plunger 2 causes the piercing component of the hollow needle 8 to fully pierce the floating plunger 5 thereby allowing the second fluid to flow outwardly from the first compartment 4 through the hollow needle 8. Movement of the push stopper 3 toward the hollow needle 8 under the action of the plunger 2 continues until all of the second fluid has been discharged from the syringe 10 through the hollow needle 8.
While eliminating the problems inherent in sequentially administering two different fluids utilizing two syringes, the device shown and described in published application US-2002-0035351-A1 involves different problems. First, the hollow needle through which the different fluids are sequentially administered must be provided with a porthole. As will be appreciated by those skilled in the art, forming a porthole in a hollow needle of the type utilized in medical syringes involves difficult and expensive manufacturing steps. Second, the axial dimensions of the hollow needle utilized in the device disclosed in the published application must be very accurately controlled. Thus, if the piercing component of the needle is too short the floating plunger will not be properly penetrated thereby preventing proper administration of the second fluid. Conversely, if the piercing component of the hollow needle is too long complete delivery of the first fluid cannot be assured.
The present invention comprises an improved syringe design which overcomes the foregoing and other problems that have long since characterized the prior art. In accordance with a first embodiment of the invention an otherwise conventional syringe is provided with a floating piston comprising upper and lower portions. The lower portion may comprise a spongy material encased in a flexible shell and having a piercing needle mounted therein. Alternatively, the lower portion may comprise a flexible shell filled with a suitable gas such as air. The upper portion comprises a seal formed from a non-coring elastomeric material.
In the practice of the first embodiment of the invention a first fluid to be administered is loaded into the barrel of the syringe below the floating piston. A second fluid to be delivered is loaded into the barrel of the syringe above the floating piston. As the plunger of the syringe is moved into the barrel, the first fluid is forced outwardly through the needle of the syringe under the action of the second fluid and the floating piston. The floating piston eventually engages the discharge end of the barrel thereby forcing the entirety of the first fluid outwardly through the needle. Continued movement of the plunger of the syringe causes the penetrating needle of the floating piston to penetrate the seal comprising the upper portion of the floating piston. At this point the second fluid is connected in fluid communication with the syringe needle through the penetrating needle of the floating piston. Further inward movement of the plunger of the syringe forces all of the second fluid outwardly through the penetrating needle of the floating piston and the syringe needle.
In accordance with a second embodiment of the invention an otherwise conventional syringe is divided into upper and lower chambers by a floating piston. The floating piston comprises a resilient, spongy material and has an aperture extending therethrough from top to bottom. The aperture may be axially disposed and circular in cross-section, however, neither the location nor the shape of the aperture is critical to the practice of the invention. A substantially rigid valve extends through the aperture of the floating piston. The upper end of the valve comprises an imperforate sealing disk. The lower end of the valve comprises an open construction to allow the passage of fluid therethrough.
The length of the valve is slightly less than the thickness of the floating piston such that the piston is normally slightly compressed thereby maintaining the sealing disk in sealing engagement with the upper end of the passageway. As the plunger of the syringe is moved axially through the barrel thereof toward the needle of the syringe, the fluid in the portion of the barrel extending above the floating piston forces the floating piston toward the needle of the syringe thereby forcing the fluid in the lower portion of the barrel of the syringe outwardly through the needle. When the floating piston bottoms out at the needle end of the syringe, further movement of the plunger compresses the spongy material comprising the floating piston thereby disengaging the sealing disk from the upper end of the passageway through the floating piston. This allows the fluid that was originally in the end of the barrel of the syringe remote from the needle thereof to pass through the aperture in the floating piston and outwardly through the needle of the syringe.